Folding machines for the above purpose are known, wherein the folding is accomplished with the help of two roller systems, one for each of two material or fabric webs. Two cooperating stacking rollers are arranged at a stacking station where the stack is to be formed during the folding process. Transport rollers and at least one cutting roller with a cutting knife are provided for each material web. Pulling rollers and guide rollers are also provided. All rollers are arranged and driven either directly or indirectly in a machine frame.
Two prepared material webs formed as an uninterrupted flow of material pieces of equal lengths that are separated or perforated from one another, are guided together and folded in a zig-zag manner or U-shaped manner. Thereby, web pieces are suitably displaced relative to one another by one half of a piece length, so that after the folding, a piece end of one piece and a piece beginning of the neighboring piece of one material web lie in the fold of the piece of the other material web.
The known machines use suction rollers as folding rollers. These suction rollers cannot produce precise fold edges, but with their help, the material pieces that are in a sequence of separated individual material pieces, can be exactly deposited on a stack, whereby folded edges are formed by pressure in the stack. A disadvantage of this operation is the relatively imprecise formation of the folding edge, the rather large stack height, and few possibilities to detect production mistakes immediately.
Other devices for producing stacks of folded and zig-zag meshed material sheets have delivery or stacking rollers with folding flaps. These folding flaps grip the material web and produce a fold edge. However, the components of the folding flaps or blades that are involved in this gripping can securely hold only one single material layer while making a fold. As a result, especially, the inner layer of the zig-zag-layered stack cannot be securely held. While the secure and good delivery of one material web can be guaranteed, the proper handling of the second material web is not assured. Therefore, such apparatus can only process endless and perforated material webs, but not material webs formed by a sequence of separated individual sheets. This conventional limit is especially applicable, where the individual sheets must have a minimum spacing of 5 mm due to technical manufacturing reasons.